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<A NAME="pgfId-186025"></A>LIFESPAN</H4>
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<A NAME="pgfId-188332"></A>The <A NAME="marker-199645"></A>LIFESPAN QoS policy allows the application to specify when a sample expires. Expired samples will not be delivered to <A NAME="marker-267979"></A>subscribers. This policy applies to the <A NAME="marker-268040"></A>topic and <A NAME="marker-268045"></A>data writer entities via the <EM CLASS="Code">
lifespan</EM>
 member of their respective QoS structures. Below is the IDL related to the lifespan QoS policy.</LI>
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<A NAME="pgfId-188135"></A><EM CLASS="Code">
</EM>
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<A NAME="pgfId-192809"></A><EM CLASS="Code">
struct LifespanQosPolicy {</EM>
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<A NAME="pgfId-188136"></A><EM CLASS="Code">
  Duration_t duration;</EM>
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<A NAME="pgfId-188269"></A><EM CLASS="Code">
}</EM>
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<A NAME="pgfId-192845"></A><EM CLASS="Code">
</EM>
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<A NAME="pgfId-192822"></A>The default value of the <EM CLASS="Code">
duration</EM>
 member is infinite, which means samples never expire. OpenDDS currently supports expired sample detection on the <A NAME="marker-268078"></A>publisher side when using a DURABILITY <EM CLASS="Code">
kind</EM>
 other than <EM CLASS="Code">
VOLATILE</EM>
. The current OpenDDS implementation may not remove samples from the <A NAME="marker-268138"></A>data writer and <A NAME="marker-268147"></A>data reader caches when they expire after being placed in the cache.</LI>
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<A NAME="pgfId-190367"></A>The value of this policy may be changed at any time. Changes to this policy affect only data written after the change.</LI>
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